Articles | Volume 5, issue 1
Regular research article
30 Mar 2016
Regular research article |  | 30 Mar 2016

A micro-capacitive pressure sensor design and modelling

Ali E. Kubba, Ahmed Hasson, Ammar I. Kubba, and Gregory Hall

Abstract. Measuring air pressure using a capacitive pressure sensor is a robust and precise technique. In addition, a system that employs such transducers lies within the low power consumption applications such as wireless sensor nodes. In this article a high sensitivity with an elliptical diaphragm capacitive pressure sensor is proposed. This design was compared with a circular diaphragm in terms of thermal stresses and pressure and temperature sensitivity. The proposed sensor is targeted for tyre pressure monitoring system application. Altering the overlapping area between the capacitor plates by decreasing the effective capacitance area to improve the overall sensitivity of the sensor (ΔCC), temperature sensitivity, and built-up stresses is also examined in this article. Theoretical analysis and finite element analysis (FEA) were employed to study pressure and temperature effects on the behaviour of the proposed capacitive pressure sensor. A MEMS (micro electro-mechanical systems) manufacturing processing plan for the proposed capacitive sensor is presented. An extra-low power short-range wireless read-out circuit suited for energy harvesting purposes is presented in this article. The developed read-out circuitry was tested in terms of sensitivity and transmission range.

Short summary
This work presents a novel design of a low power high-temperature MEMS elliptical capacitive pressure sensor that can be utilized within wireless sensor systems, e.g. TPMS. Throughout numerical and analytical analysis, it was found that sensor sensitivity and temperature resistance could be increased if the diaphragm area has two symmetrical segments of chords parallel to the major axis removed, and if diaphragm deformation increases the separation distance between the sensing capacitor plates.